PHOTODYNAMIC INACTIVATION OF PATHOGENIC BACTERIA IN BIOFILMS USING NEW SYNTHETIC BACTERIOCHLORIN DERIVATIVES

Bacteriochlorins as the antimicrobial photosensitizers have a promising future in the face of the unrelenting increase in antimicrobial resistance. The goal of this study was to investigate the infl uence of lipophilicity and number of positively charged substituents in these molecules on the photodynamic inactivation (PDI) of biofi lm bacteria in vitro. Testing how bacteriochlorin derivatives with different properties affect microbes will allow to determine the optimal ratio of these parameters within a single molecule. We have investigated 4 bacteriochlorin derivatives, all of which were synthesized in Organic Intermediates and Dyes Institute. These were: hydrophobic neutral meso-tetra(3-pyridyl) bacteriochlorin (ВС1), amphyphilic tetracationic meso-tetra(1- undecyl-3-pyridyl)bacteriochlorin tetrabromide (ВС2), hydrophilic tetracationic meso-tetra[1-(4'-bromobutyl)-3-pyridyl]bacteriochlorin tetrabromide (ВС3) and octacationic meso-tetra[1-(4'-pyridiniobutyl) -3-pyridyl]bacteriochlorin octabromide (ВС4) . The water-soluble cationic bacteriochlorin derivatives showed the most effective PDI of bacteria in biofi lms. While tetracationic BC3 caused total inactivation of S. aureus 15, octacationic BC4 was bactericidal for P. aeruginosa 32 to the same degree (>99.999%). Interestingly, increasing the number of cationic substituents from 4 to 8 in bacteriochlorin molecules enhances bactericidal action against gram-negative bacteria in biofi lms. The lack of charge-carrying groups and high degree of lipophilicity of PS have negative impact on PDI of biofi lm bacteria. Bacterial membrane damage as a result of PDI can be one of the causes of cell death.